1. Field of the Invention
The invention relates to a hinge used in a note-type computer, and more particularly to a hinge used for rotatably connecting a keyboard to a display screen.
2. Description of the Related Art
FIG. 1 is a cross-sectional view of a conventional hinge used in a note-type computer.
The illustrated hinge is used for rotatably connecting a display screen 10 to a keyboard 11. The hinge is comprised of a L-type support 12, a rotation shaft 13, and a nut 14.
The L-type support 12 is fixed onto the keyboard 11 by means of a bolt 15. The L-type support 12 is formed with a through-hole (not illustrated) at a standing portion 12a. 
The rotation shaft 13 is fixed at one end to the display screen 10, and extends at the other end through the through-hole of the standing portion 12a of the L-type support. The rotation shaft 13 is formed at the other end with a threaded portion 13a. The rotation shaft 13 is rotatably fixed to the standing portion 12a of the L-type support 12 by threading the nut 14 into the threaded portion 13a of the rotation shaft 13 with a first washer 16, a wave spring 17 and a second washer 18 all being sandwiched between the standing portion 12a and the nut 14.
A third washer 19 is inserted around the rotation shaft 13 between the standing portion 12a of the L-type support 12 and the display screen 10.
In operation, the rotation shaft 13 is rotated relative to the keyboard 11. For instance, the rotation shaft 13 may be rotated such that the display screen 10 overlaps the keyboard 11, or the rotation shaft 13 may be rotated such that the display screen 10 perpendicularly stands relative to the keyboard 11.
FIG. 2 is a cross-sectional view of another conventional hinge used in a note-type computer. The illustrated hinge is suggested in Japanese Utility Model No. 3040939 published on Sep. 5, 1997 in Japan.
The illustrated hinge is used for rotatably connecting a display screen 20 to a keyboard 21. The hinge is comprised of a support 22 having a cylindrical portion 22a, a rotation shaft 23, a nut 24, and a spring 25.
The support 22 is fixed onto the keyboard 21 by means of a bolt 29. The support 22 is formed with a through-hole 26 throughout the cylindrical portion 22a in a length-wise direction thereof The through-hole 26 is comprised of a tapered hole 26a and a straight hole 26b. 
The rotation shaft 23 is fixed at one end to the display screen 20, and extends through the through-hole 26 of the support 22. The rotation shaft 23 is designed to have a tapered portion 23a and a straight portion 23b in conformity with the tapered hole 26a and the straight hole 26b. The rotation shat 23 is formed at the other end with a threaded portion 23c. The rotation shaft 23 is rotatably fixed to the support 22 by threading the nut 24 into the threaded portion 23c of the rotation shaft 23 with the spring 25 and a washer 27 both being sandwiched between the support 22 and the nut 24.
A frictional sheet 28 is adhered to an inner surface of the tapered hole 26a such that the frictional sheet 28 provides frictional force to the tapered portion 23a of the rotation shaft 23.
A hinge used in a note-type computer has been required to be smaller and smaller in size and lighter and lighter in weight in order to ensure a user to readily carry a note-type computer.
On the other hand, a display screen has been designed to be wider and wider to ensure a user to readily observe what is displayed. Accordingly, a display screen increases its weight.
Thus, a hinge used in a note-type computer is now required to be small in size, light in weight, and have a strength sufficient to support a display screen which gradually increases its weight.
However, in the conventional hinges illustrated in FIGS. 1 and 2, since the L-type support 12 and the support 22 are formed by zinc die-casting. Accordingly, they are heavy, and cannot be formed thin because of its low strength.
Hence, the conventional hinges cannot meet with the above-mentioned requirement.
In view of such a problem in the conventional hinges, it is an object of the present invention to provide a hinge used in a note-type computer which hinge is smaller and lighter than the conventional one, and has a greater strength than that of the conventional one to thereby ensure a greater upper limit in the rotation number than that of the conventional one.
There is provided a hinge rotatably connecting a first body to a second body, including (a) a main body to be fixed onto the first body, the main body including a hollow cylindrical portion horizontally extending, (b) a rotation shaft fixed at one end to the second body and rotatably connected at the other end to the main body, and (c) a frictional collar filling space therewith between the rotation shaft and the hollow cylindrical portion of the main body.
There is further provided a hinge rotatably connecting a first body to a second body, including (a) a main body to be fixed onto the first body, the main body including a hollow cylindrical portion horizontally extending, (b) a rotation shaft fixed at one end to the second body and rotatably connected at the other end to the main body, (c) an outer collar connected to the hollow cylindrical portion of the main body in a direction in which the hollow cylindrical portion extends, and (d) a frictional collar filling space therewith between the rotation shaft and both the outer collar and the hollow cylindrical portion.
It is preferable that the hinge further includes a nut, and wherein the main body further includes a wall portion covering one of sides of the hollow cylindrical portion therewith and being formed with a through-hole, in which case, the rotation shaft passes through the through-hole of the wall portion at the other end, and rotatably fixed to the wall portion by means of the nut.
It is preferable that the cylindrical hollow portion has a reduced diameter portion at a distal end thereof and the outer collar is a cylindrical collar having an inner diameter equal to an outer diameter of the reduced diameter portion of the cylindrical hollow portion.
It is preferable that the cylindrical hollow portion has at least one stepped portion on the reduced diameter portion, the stepped portion having a greater outer diameter than an outer diameter of the reduced diameter portion, in which case, the outer collar is formed at one end thereof with a cut-out into which the stepped portion is to be fit.
For instance, the stepped portion may be rectangular in shape.
It is preferable that the cylindrical hollow portion has two stepped portions, and the outer collar is formed at one end thereof with two cut-outs into which the stepped portions are to be fit, in which case, the two stepped portions are spaced away from each other preferably by 180 degrees.
It is preferable that the rotation shaft has a tapered portion surrounded by the outer collar and the cylindrical hollow portion.
For instance, the outer collar is made of stainless steel, the frictional collar is made of plastic, and the rotation shaft is made of stainless steel.
It is preferable that the frictional collar is made of material having spring characteristic.
It is preferable that the nut provides a resistance of about 7 kg/cm to said rotation shaft, when the rotation shaft is rotated.
It is preferable that the rotation shaft is formed at outer surface of the tapered portion with at least one recess in which lubricant is pooled, in which case, the recess extends preferably in a length-wise direction of the rotation shaft.
As an alternative, the frictional collar may be formed at inner surface at which the frictional collar makes contact with the tapered portion of the rotation shaft, with at least one recess in which lubricant is pooled, in which case, the recess extends preferably in a length-wise direction of the rotation shaft.
For instance, the first body may be a keyboard, and the second body may be a display screen in a note-type computer.
The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings.